1. Field of the Invention
This invention relates to sidewall structures employed in cargo containers, truck trailers and so on, and more particularly, to a post construction used in such sidewalls.
2. Description of the Prior Art
Cargo containers are used to transport goods by ship, rail and truck. The containers typically are large metal boxes with doors at one end. On ships and rail cars the containers are stacked one over the other. To transport the containers to terminals requires the containers to be placed on a trailer chassis from either the ship or rail car and hauled by truck tractor to a point of destination.
The containers of the prior art are generally similar in construction. Some containers comprise relatively thick steel sheet metal for withstanding stacking loads. These are relatively heavy and utilize large amounts of metal making them costly. Other more widely used containers comprise roof and floor frames wherein the roof frame is supported by a pair of upright intermediate frames on each side. See for example, U.S. Pat. No. 3,646,609 ('609). A relatively thinner sidewall construction is then connected to and between the intermediate frames. Corner posts support the roof frame at each corner and short sections of sidewall are connected between each intermediate frame and a corner post. The intermediate frames have metal castings or fittings at the lower and upper ends. The upper castings or fittings are adapted to receive crane lifting jaws and male alignment members for aligning an upper container stacked thereon.
The lower castings or fittings mate with the upper ones of a lower stacked container or support members such as at the bottom of a rail car well receiving the lower container. The intermediate frame members support the load of an upper stacked container. See for example the aforementioned copending application. The side panels forming the sidewall in an all metal construction comprise relatively thin sheets, e.g., 0.025-0.50 inch (0.635-127 mm) thick aluminum. These are fastened in overlapping relation by rivets or in abutting edge relation as shown for example in U.S. Pat. No. 4,685,721 wherein the edge portions of the side sheet plates are riveted to a securing panel. A sealant is disclosed between the securing panel and the sheet plates at the rivets. Periodically horizontally spaced hat shaped reinforcing ribs vertically oriented between the floor and roof frames are riveted to the sidewall panels. See U.S. Pat. No. 3,646,609 for example. U.S. Pat. No. 2,384,965 shows corrugated sheets in the alternative to the hat shaped ribs.
Other insulating containers have thick insulating walls sandwiched between thin outer metal sheets which are also fastened to the intermediate frames. Plywood sheets are typically fastened to the interior surface of the side panels of the container or to spacer ribs in the interior. The plywood sheets protect the side panels from damage caused by the cargo during transport or during load and unload, the panels being relatively thin and thus damage relatively easily exhibiting dents or even punctures. See U.S. Pat. No. 2,384,965 for interior linings in a vehicle body construction in truck trailers. Truck trailers are constructed similarly but without the intermediate frames utilized in the container configuration.
A further problem occurs when containers are transported in rail cars. These cars have wells which closely receive the containers. The side panels, in all metal configurations, however, due to cargo transverse loading, as recognized by the present inventors, bow outwardly near their floors. This bowing causes the side panels to interfere with the rail car sides forming the well and damages the side panels during loading or unloading of the containers from the rail car and also during transport. This damage can require premature replacement of the container.
The use of additional plywood which needs to be periodically replaced due to damage and the damaging of the metal side panel sheets is costly as well as the cause of unsightly damage. The present inventors recognize a need to provide an improved cargo container and the like which is less likely to damage in use and is less costly then prior art structures.